Solid matter such as weeds and jelly fish floating or submerged in water can be a considerable nuisance when the water is to be used for a special purpose for example sea water in a desalination plant, or fresh water for cooling in manufacturing plant process.
The water intake ducts used for such purposes are usually provided with filters for screening unwanted solid matter before the water reaches its destination.
However, the use of filters does not entirely solve the problem because certain solid matter is able on occasions to get past the filters and in the case of tar balls for example the filters themselves merely become blocked.
Further algae and such other weed growth tend to block intake filters in certain parts of the world.